1. Field of the Invention
The present invention relates to rider control systems for propulsive wings and sport traction kites. More particularly the present invention relates to a kite control bar adapted with an internal outside-line sheeting system that functions to allow the rider to selectively increase and/or decrease tension on the outer control lines so as to control the resulting angle of attack of the kite.
2. Description of Related Art
The use of kites as a means of propulsion, e.g. traction kites, has existed for over a century. Kites were first used as a means of propulsion in pulling boats. Though already popular water and land based board sports such as surfing and snowboarding, the sports of kiteboarding and snow kiting have grown. These sports adapt the principals of surfing and snowboarding to include kites as a method for generating speed. Kitesurfing is done in the water, snowkiting is done on the snow with skis or a snowboard, and landboarding is done on the land on a mountain board. Generally speaking, if one stands on a board and uses a kite to be pulled along by the wind, it's kiteboarding. A number of advances, particularly to the design of the kite propulsion system, have led to improvements in safety, increases in top attainable speeds, and improvements in overall performance.
Most traction kites currently used in kiteboarding are constructed with flexible canopy having an inflatable leading edge armature which distributes dynamic loads via ropes connected to the leading edge. As used therein the terms “traction kite” or “kite” shall mean a propulsive wing that harnesses wind power to pull a rider through the water, snow, or other environment typically with a riding platform (e.g. a kite board, snow board, landboard, or other riding apparatus). An example of a basic traction is described in U.S. Pat. No. 4,708,078, issued to Legaignoux et al., which discloses a basic design for a leading edge inflatable (“LET”) kite. Legaignoux discloses traction kite having an inflatable leading edge having an inflatable armature covered by a flexible envelope.
As kite sports have evolved, demand for kites with improved performance characteristics has grown. Specifically, kite users desire kites with improved power, handling, control, improved/faster turning speeds, and enhanced control response achieved with minimal user input force. As a result, the art reveals advancements in LEI kite design. One common LEI traction kite is referred to as the “C-Kite”. The C-Kite is a common kite design that has been in use for many years. The C-Kite is named for the arc-like shape it forms while in flight which resembles the letter “C”. The control line configuration for the C-Kite generally includes the attachment of four lines to the four corners of the kite which cause the kite to arc sharply while in flight. When viewed from above/overhead, the C-kite characteristically forms a convexly shaped trailing edge. A slight variation of the C-kite is the 5th line C-kite which includes an extra line attached at the middle of the leading edge of the kite. The purpose of the 5th line is to assist the rider in de-powering and re-launching the kite. De-powering is essentially a changing the aerodynamic characteristics of the kite and provides a safety procedure for the rider that reduces the propulsive surface area thereby reducing the force of the wind on the kite and the lines.
A more recent innovation in LEI traction kite design was the introduction of the “Bow Kite”. The Bow Kite has two defining characteristics which differentiate it from the C-kite, including: 1) the trailing edge of the Bow Kite is concave; and 2) the Bow Kite is controlled by a series of control lines attached to the leading edge, commonly referred to as a bridle. The bridle is affixed to the leading edge and tips of the kite in a web-like fashion and causes the kite to possess a flatter shape (i.e. less leading edge curvature or arc) when in flight. The concave trailing edge and the addition of the bridle to the leading edge of the kite allow the kite to be de-powered with ease thus eliminating the need for a separate 5th line. Furthermore, these features allow the Bow Kite to be adaptable to varying wind speeds, whereas the C-kite's design is better suited for specific wind speeds. U.S. Pat. No. 7,374,133, issued to Legaignoux, provides an example of a conventional Bow Kite. Even more recently hybrid kites have been produced which combine elements of both the C-kite and the Bow Kite. Although there are various forms of hybrid kites, all of them generally have a convex trailing edge and a leading edge bridle. The convex trailing edge is adapted from the C-kite and the leading edge bridle and bow configuration is adapted from the Bow Kite. The hybrid kite achieves a middle ground between the C-kite and the Bow Kite. It possesses a greater ability to de-power than the C-kite, but also allows for a greater performance and turning capability than the Bow Kite.
All of the above-referenced kites are typically controlled by the rider using a control bar having a plurality of lines affixed to the kite. By manipulation of the control bar and adjustment of tension on the lines, as well as line length, the rider is able to turn the kite as well as power and depower the kite. It is well known that the traction force (i.e. power) generated by a traction kite is largely dependent upon the angle of attack. The “Angle of Attack” (“AOA”) is the angle at which the kite flies in relation to the wind. Generally speaking, increasing the angle of attack generates more lift and results in increased power, whereas decreasing the angle of attack generates less lift and results in decreased power. Accordingly, providing the rider with improved control is important in the sport of kite boarding.
One common control requirement involves the need to sheet or trim the kite. Sheeting mechanisms generally function to allow the kite operator to adjust the length of certain control lines so as to alter the angle of attack or pitch of the kite. Most traction kite sheeting systems function by requiring the rider to adjust central lines connected to the leading edge of the kite. For example, U.S. Pat. No. 6,877,697, issued to Bellacera, discloses kite control systems having a sheeting mechanism including a sheeting spool for one or more central sheeting lines which extend to the leading edge of the kite, and a sheeting regulator wrapped circumferentially around the sheeting spool. Rotation of the sheeting spool determines the deployed length of the sheeting lines.
U.S. Pat. No. 7,036,771, issued to Pouchkarev, discloses a kite control and depowering device wherein a control flying bar includes a continuous trim and safety flying line disposed at their lower ends over a rapid depowering apparatus. The depowering apparatus includes means for capturing and rapidly releasing an expansion disposed on the trim line, such that when rapid depowering is required, a simply release mechanism may be actuated to change the angle of attack of the airfoil rapidly.
U.S. Pat. No. 7,182,294, issued to Blackman, discloses a kite surfing bar wherein tension on the central lines may be adjusted via a system wherein the central lines are routed through the interior of the control bar via pulleys.
U.S. Pat. No. 7,581,701, issued to Logosz et al., discloses a kite control device including a bar having a fixed trim adjustment centrally located between the bar and the user to provide a safety depower function. Sheeting is accomplished by sliding the control bar up and down an adjustable chicken loop line system. U.S. Pat. No. 7,621,485, issued to Logosz et al., discloses a kite control system having a central trim line connected to the leading edge. The trim line is adjustable to allow the user to adjust and mechanically fix the length of the trim line while the kite is in flight. Similar control schemes are disclosed in Patent Application Publications Nos. US 2007/0120016 (Eberle et al.) and US 2008/0035796 (See et al.).
Kite control systems that accomplish trim and/or sheeting control using center lines attached to the leading edge (i.e. center line sheeting systems) all suffer from a number of significant disadvantages. One such disadvantage relates to safety. More particularly, if a center line sheeting system slips, the angle of attack can unexpectedly increase thereby causing the kite to power-up which can cause the rider to lose control. In addition, center line sheeting systems become difficult to adjust when the lines become twisted thereby inhibiting the rider's ability to control the kite. Accordingly, there exists a need for an improved kite control system that avoids the limitations and disadvantages present in the art.